This invention relates to a door closer and particularly relates to a door closer with facility for allowing the related door to swing to a relatively wide opening with relative ease before opposition to further opening of the door is increased.
Door closers typically are formed by a cylinder which is coupled to a spring tube to form an enclosed main chamber containing fluid (e.g. oil) within the cylinder and tube. A piston is located within the cylinder for movement within the chamber. At least one coil spring is located within the tube portion of the chamber and is in axial engagement with one end of the piston to normally urge the piston into the cylinder portion of the chamber when the associated door is closed.
An elongated opening is formed through the piston and extends from near one end of the piston to near the other end thereof. One side wall of the elongated opening is formed with teeth to form a rack. A pinion is located within the elongated opening so that the teeth of the pinion mesh with the teeth of the rack.
Driving elements are formed on opposite sides of the pinion and extend through the sidewall of the cylinder to allow coupling of the driving elements and the pinion to facilities external of the cylinder.
A door closer of this type can be mounted on one surface of a door near the top where one of the driving elements is coupled to one end of a first linkage arm. The other end of the first arm is coupled to one end of a second linkage arm for hinged movement relative coupled for pivotal movement to a bracket which is fixedly secured to the door frame.
When the door is in the closed position, the linkage arms are positioned so that the spring is urging the piston into the end of the cylinder portion of the chamber which is furthest from the spring tube. As the door is opened, the linkage arms are moved so that the first arm causes the driving element and pinion to rotate about the axis of the pinion. As the pinion rotates, the mesh of the pinion and rack teeth cause the piston to move against the biasing action of the spring and toward the tube portion of the chamber.
A reserve chamber or reservoir is formed in the cylinder and communicates with the main chamber through a main passageway and a back-check passageway of restricted opening formed in the cylinder wall. As the piston is moved upon opening of the door, some of the fluid is initially urged from the main chamber through the main passageway and the back-check passageway of restricted opening and into the reservoir. Eventually, the piston is moved sufficiently to cover the main passageway whereby the fluid now travels only through the back-check passageway into the reservoir. This condition occurs, for example, when the door is opened about sixty-five to seventy degrees from a closed position. The fluid now begins to be compressed within the main chamber with the only outlet being through the back-check passageway and thereby provides a "back check" condition to prevent the door from being swung open too swiftly.
A door closer of the type described above is also described and claimed in applicant's copending U.S. patent application identified by Ser. No. 07/738,636, filed on Jul. 31, 1991.
Due to certain conditions involving use of the door with the door closer, one may wish to be able to more freely open the door by a greater amount before the back-check condition is effected. For example, it may be desirable to open the door with relative ease to a position greater than ninety degrees from the closed position to allow those passing through the door portal to move without the increased opposition to opening of the door which is encountered when the back-check condition is effected.
Thus, there is a need for a door closing having facility for allowing the related door to be opened with relative ease to a position greater than ninety degrees and prior to any increased opposition to the opening of the door by the occurrence of the back-check condition.